package com.hmdp.utils;


import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;


@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    //缓存穿透方法封装
    public <R,ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.redis中查询
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.存在就返回
        if(StrUtil.isNotBlank(json)){

            return JSONUtil.toBean(json, type);
        }
        //判断是否为空字符串
        if (json !=null){
            return null;
        }
        //3.不存在，从数据库中查询
        R r = dbFallback.apply(id);
        //4.不存在，返回错误信息
        if(r == null){
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //5.存在，将数据写入redis缓存并返回数据
        this.set(key, r, time, unit);
        return r;
    }


    //逻辑过期解决缓存穿透
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public <R, ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.redis中查询
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.不存在，返回null
        if(StrUtil.isBlank(json)){
            return null;
        }
        //3.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //4.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //4.1未过期，直接返回店铺信息
            return r;
        }
        //4.2已过期，需要缓存重建
        //5.缓存重建
        //5.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //5.2判断是否获取锁成功
        if(isLock){
            //5.3成功，开启独立线程，实现缓存重建
            if (expireTime.isAfter(LocalDateTime.now())) {
                //再次检测redis缓存是否过期，未过期，直接返回店铺信息
                return r;
            }
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key, r1, time, unit);

                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //6.4失败，返回过期的商品信息
        return r;
    }

    //尝试获取锁
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //释放锁
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }




}
